Connection for well bore drilling tools

ABSTRACT

A drilling tool connection includes a male pin, a female box connector, and a locking pin. The male pin includes a hexagonal outer perimeter, at least a portion of the pin having a cylindrical bore along a longitudinal axis of the pin, where the pin has a transverse slot formed transverse to the longitudinal axis of the pin. The box connector element includes a circular outer perimeter, where at least a portion of the box connector element has a hexagonal aperture aligned with a longitudinal axis of the box. The box connector element has at least one transverse bore formed in the box transverse to the longitudinal axis of the box, and the hexagonal aperture of the box is adapted to receive the hexagonal portion of the male pin. The locking pin is insertable through an aperture defined by the slot of the pin and the bore of the box.

TECHNICAL BACKGROUND

This disclosure relates to well bore equipment and, more particularly, to connections for various downhole tools used for drilling well bores.

BACKGROUND

Downhole drilling motors have been used for many years in the drilling of oil and gas wells and other wells. In a usual mode of operation, the rotational power output shaft of the motor and the drill bit will rotate with respect to the housing of the motor. The housing, in turn, is connected to a conventional drill string composed of drill collars and sections of drill pipe. This drill string extends to the surface. Drilling fluid is pumped down through the drill string, to the bottom of the hole and back tip the annulus between the drill string and the wall of the bore hole. The drilling fluid cools the drill bit and removes the cuttings resulting from the drilling operation.

Since the inception of downhole drilling motors, the rotational power output from the motors has increased. The rotational power output of the motor is transferred to the drill bit, in typical fashions through a tool joint, which may couple the output drilling motor to the drill bit or other appropriate sections of a downhole drilling apparatus. In certain instances, the tool joint may employ a threaded connection, such as a male/female API or other threaded tapered connections. Such types of connections may be designed to handle the mechanical stress and shear force associated with drilling operations. These connections, however may encounter forces and resistance within the well bore that are greater than those forces for which they are designed. For example, rotational torque output from a drilling motor may generate a shear force on the tool joint. Typically, such a shear force, if great enough, may cause the tool joint to fail (e.g., shear off at various threaded connections). Further, due to the nature of threaded connections, the rotational torque may cause such a connection to decouple (e.g., unscrew) apart from a mechanical failure.

One or more components of a downhole drilling apparatus may come uncoupled and are lost or stuck in the well bore due to tool joint failure. For instance, drill bits, downhole motors, impact jars, MWD/LVD or sections thereof are commonly among the downhole drilling components lost in the well bore, possibly requiring the initiation of “fishing” operations (i.e., downhole tool retrieval) for the lost tool.

SUMMARY

This disclosure relates to well bore equipment and, more particularly, to connections for various downhole tools used for drilling well bores.

In accordance with one general implementation, a drilling tool connection includes a male pin connector element, a female box connector element, and a locking pin. The male pin connector element is disposed on a first downhole drilling device and includes a substantially hexagonal outer perimeter, at least a portion of the pin having a substantially cylindrical bore along a longitudinal axis of the pin, where the pin has at least one transverse slot formed transverse to the longitudinal axis of the pin. The female box connector element is disposed on a second downhole drilling device and includes a substantially circular outer perimeter, where at least a portion of the box connector element has a substantially hexagonal aperture aligned with a longitudinal axis of the box. The female box connector element has at least one transverse bore formed in the box transverse to the longitudinal axis of the box, and the substantially hexagonal aperture of the female box is adapted to receive the substantial hexagonal portions of the male pin connector element. Tile locking pin is insertable through an aperture defined by the at least one transverse slot of the pin and the at least one transverse bore of the box upon alignment of the transverse slot with the transverse bore.

In some specific aspects, the substantially cylindrical longitudinal aperture may be adapted to direct drilling fluid through the second downhole drilling device. Further, the locking pin may be substantially cylindrical. The drilling tool connection may further include all end cap configured to fasten to the locking pin and substantially prevent the locking pin from being removed from the aperture defined by the first slot and the second slot. In certain aspects, the drilling tool connection further includes an end cap configured to fasten to the aperture formed by the transverse slot and the transverse bore by a threaded connection. The aperture defined by the transverse slot and the transverse bore may be substantially cylindrical.

In certain aspects, the drilling tool connection may include a first box seal disposed within a box seal groove, where the box seal groove may be formed in an interior surface of the box defining the substantially hexagonal aperture. In some aspects, the locking pin may be a first locking pin and the drilling tool connection further includes a second transverse slot formed proximal to the distal end of the pin transverse to the longitudinal axis of the pin; a second transverse bore formed in the box transverse to the longitudinal axis of the box; and a second locking pin insertable through a second aperture defined by the second transverse slot and the second transverse bore upon alignment of the second transverse slot with the second transverse.

In specific aspects, the first and the second downhole drilling devices may be selected from the group consisting of a downhole drilling motor; a stabilizer; a universal joint assembly; a drill bit; a drill collar; a drill pipe; or a bearing mandrel. Additionally, the female box connector element may further include a shoulder formed in the box at a distal end of the substantially hexagonal aperture while the pin may further include a substantially planar surface formed at the distal end of the pin. The male pin connector element may be configured to transmit thrust to the shoulder substantially parallel to the longitudinal axes of the pin and the box.

In another general implementation, a male pin disposed on a first downhole drilling device, a female box connector element, and a locking pin. The male pin includes a pin perimeter of a first geometric shape, where at least a portion of the pin has a substantially cylindrical bore along a longitudinal axis of the pin. The male pin has at least one transverse slot formed in the pin perimeter transverse to the longitudinal axis of the pin. The female box connector element is disposed on a second downhole drilling device with at least a portion of the box having a box aperture of a second geometric shape aligned with a longitudinal axis of the box. The box aperture is adapted to receive the first geometric shape portion of the male pin and has at least one transverse bore formed in the box transverse to the longitudinal axis of the box. The locking pin is insertable into an aperture defined by the at least one transverse slot of the pin and the at least one transverse bore of the box upon alignment of the transverse slot with the transverse bore.

In some specific aspects, tile first and second geometric shapes may be one of a hexagon; an octagon; a nonagon; or a decagon. Further, the longitudinal aperture may be adapted to direct drilling fluid through the second downhole drilling device. Also, the well bore tool coupling device may include an end cap configured to fasten to the locking pin and substantially prevent the locking pin from being removed from the aperture defined by the first slot and the second slot. The device may include an end cap configured to fasten to the aperture formed by the slot and transverse bore by a threaded connection. In certain aspects, the aperture defined by the slot and the transverse bore may be substantially cylindrical.

The well bore tool coupling device may also include a first box seal disposed within a box seal groove, where the box seal groove may be formed in an interior surface of the box defining the box aperture. Further, the locking pin may be a first locking pin, and the well bore tool coupling device may further include a second transverse slot formed at tile distal end of the pin transverse to the longitudinal axis of the pin; a second transverse bore formed in the box transverse to the longitudinal axis of the box; and a second locking pin insertable through a second aperture defined by the second transverse slot and the second transverse bore upon alignment of the second slot with the second transverse bore. The female box connector element may further include a shoulder formed in the box at a distal end of the aperture of the second geometric shape and the pin may further include a substantially planar surface formed at the distal end of the pin and configured to transmit thrust to the shoulder substantially parallel to the longitudinal axes of the pin and the box. The female box connector element may also include a ledge proximate to a distal end of the box.

Various implementations of a drilling tool connection according to the present disclosure may include one or more of the following features. For example, the drilling tool connection may be able to withstand greater rotational torque as compared to other types of threaded tool joints, thereby decreasing a possibility of mechanical failure or shearing. As another example, the drilling tool connection may allow for greater time and cost efficiency in assembling a downhole tool apparatus for drilling operations. As a further example, the drilling tool connection may allow for a downhole tool to remain coupled to, for example, another downhole tool such as a downhole drilling motor or drill bit, a drill string section, or a universal joint assembly. As yet another benefit, the drilling tool connection may be substantially free of stress risers and galling as encountered in threaded connections, thereby allowing greater torque to be output by the downhole drilling motor without mechanical failure in the drilling apparatus. Further, the drilling tool connection may allow for a greater axial force to be applied to a downhole drilling apparatus by the drill string in attempting to back off the apparatus from the well bore, thereby increasing the likelihood that the apparatus may be removed from the well bore. The drilling tool connection may, therefore, decrease the number of fishing trips down the well bore to recover lost downhole tools.

These general and specific aspects may be implemented using a device, system or method, or any combinations of devices, systems, or methods. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and front the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a downhole drilling apparatus incorporating a drilling tool connection in accordance with the present disclosure;

FIG. 2A illustrates a male end of a drilling tool connection in accordance with the present disclosure;

FIG. 2B illustrates a portion of a downhole drilling apparatus incorporating a female end of a drilling tool connection in accordance with the present disclosure:

FIG. 2C illustrates a locking pin of a drilling tool connection in accordance with the present disclosure;

FIG. 3 illustrates the male connector of FIG. 2A assembled to the female connector of FIG. 2B with the locking pin of FIG. 2C; and

FIG. 4 illustrates one method of assembling a drilling tool connection in accordance with the present disclosure.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

A drilling tool connection may be used to couple together various downhole drilling devices, such as downhole drilling motors, impact jars, MWD/LWD tools, drill bits, universal joint assemblies, bearing sections, drill string sections, and the like. The drilling tool connection, generally, includes a male end with an elongated pin including a longitudinal bore disposed along a longitudinal axis of the pin; a female end with a box including an aperture designed to receive the pin, and one or more locking pins designed to be inserted through apertures in the wall of the box into a semi-circular pin slot on the exterior surface of the pin, thereby securing the pin and the box together. The pin includes one or more transverse pin slots while the box includes one or more corresponding transverse semi-cylindrical box bores, such that upon insertion of the pin into the box, cylindrical apertures are created by alignment of the transverse pin slots with the corresponding transverse box bores. The drilling tool connection also includes one or more end caps designed to be secured to each end of the locking pins, thereby substantially preventing the locking pins from being unintentionally removed from the apertures during a drilling/retrieving operation (e.g., by rotational inertia).

In operation, the pin may transmit rotational torque to the female box through an outer surface flats of the pin in contact with the aperture designed to receive the pin in the box. Further, the pin may transmit an axial thrust force to the box at a shoulder of the box proximate to one end surface of the pin. Additionally, the locking pins of the drilling tool connection may be designed to withstand a shear force applied to such locking pins upon removal of the downhole drilling devices from a well bore.

FIG. 1 illustrates a downhole drilling apparatus 100 incorporating a drilling tool connection 135 in accordance with the present disclosure. Downhole drilling apparatus 100, typically, is used to form a well bore 105 through one or more subterranean formations, such as shale, sandstone, coal, or other geologic zones occurring at sub-surface depths. Such zones may be desirable to access from the surface due to deposits of petroleum natural resources (e.g., oil, natural gas) contained therein. In some aspects, the downhole drilling apparatus 100 may be used as a directional drilling apparatus to form directional (e.g., horizontal, slant) well bores. The downhole drilling apparatus 100 includes a drill string 115, a downhole drilling motor 125 (partially shown in FIG. 1), a universal joint assembly 120, and one or more drilling tool connections 135. The downhole drilling apparatus 100, generally, also includes a drilling fluid 130 flowing through the drill string 115 and also the sections of the drilling apparatus 100 toward a drill bit section (not shown) coupled to a distal end of the downhole drilling apparatus 100. In typical embodiments of the downhole drilling apparatus 100, the aforementioned apparatus sections and any other appropriate sections are connected to the drill string 115. The drill string 115 generally consists of multiple sections of threaded pipe anchor threaded drill collars coupled to each other and extending to the surface.

In order to advance the downhole drilling apparatus 100 further into the sub-surface zones to form the well bore 105 to a specified depth, drilling fluid 130 is typically pumped in a central bore 111 from the surface through the drill string 115. The drilling fluid 130 may be different substances depending on, for instance, the application of the downhole drilling apparatus 100, the subterranean zones being penetrated by the downhole drilling apparatus 100, and the pressure of such zones relative to the pressure of the drilling fluid 130. For example, the drilling fluid 130 may be air, a mixture of air and water, water, “drilling mud,” such as water or other fluid mixed with a polymer or clay substance, or a form of synthetic fluid, to name but a few. Drilling fluid 130 is used for several purposes, namely, to provide hydraulic power to the downhole drilling motor 125 (as described below), cool and lubricate the drill bit section as it cuts through the geologic formation being drilled, and remove the drilled formation cuttings to the surface. For instance, once the drilling fluid 130 exits the drill bit section and picks up the formation cuttings (e.g., bits of rock), the drilling fluid 130 travels back to the surface via the annulus 110 between the downhole drilling apparatus 100 and the well bore 105.

The downhole drilling motor 125, generally, supplies rotational power that is transferred to the drill bit section through one or more drilling tool connections 135 and the universal joint assembly 120, such rotation allowing the drill bit section to create the well bore 105. The rotational power supplied by the drilling motor 125 may be generated by the drilling fluid 130, which is pumped at a specified flow rate through the drill string 115 and into the drilling motor 125. The drilling motor 125 may include a rotor that is turned by the flowing drilling fluid 130 at a speed proportional to the volume of the drilling fluid 130 passing through the drilling motor 125. In some embodiments, the drilling motor 125 may be a moineau-style downhole motor power section or alternatively, a turbine-style downhole motor.

The universal joint assembly 120 is coupled between the drilling motor 125 and the drill bit section. The universal joint assembly 120 may convert eccentric rotation from the drilling motor 125 to concentric rotation to supply to the drill bit section. The universal joint assembly 120 is coupled to the drilling motor 125 and the drill bit section via drilling tool connections 135. Alternatively, the universal joint assembly 120 may be coupled to one or more drilling sections via another connection, such as a threaded connection.

The drilling tool connections 135 couple together various sections of the downhole drilling apparatus 100. For example, as illustrated in FIG. 1, a drilling tool connection 135 may couple the downhole drilling motor 125 to an up-hole device (e.g., a impact jar, MWD/LWD tool, drill collar), as well as the universal joint assembly 120. A drilling tool connection 135 may also couple the universal joint assembly 120 to, for example, a bearing section (not shown). A drilling tool connection 135 may also couple a bearing section of the downhole drilling apparatus 100 to the drill bit section. Generally, the drilling tool connection 135 transmits rotational torque generated by the downhole drilling motor 125 to another downhole drilling tool, such as the drill bit section. Further, the drilling tool connection 135 may allow for multiple downhole drilling devices to remain coupled together when withdrawing the downhole drilling apparatus 100 from the well bore 105.

In some embodiments of the downhole drilling apparatus 100, the drilling tool connection 135 may be utilized in place of a more traditional coupling technique, such as, for example, a threaded connection (e.g., male/female NPT). In such embodiments, the drilling tool connection 135 may allow the coupled drilling tools to remain coupled even when resistance is encountered by the drilling apparatus (e.g., a counter-directional torque on the drill bit).

FIGS. 2A-C illustrate particular components of a drilling tool connection in accordance with the present disclosure. More specifically, FIGS. 2A-C illustrate a male pin 205, a female box 225, and a locking pin 265 (respectively), which, in part, combine to form the drilling tool connection. The drilling tool connection formed in part by the male pin 205, the female box 225, and the locking pin 265 may be utilized as the drilling tool connection 135 in the downhole drilling apparatus 100 shown in FIG. 1. Alternatively, the drilling tool connection formed in part by the male pin 205, the female box 225, and the locking pin 265 may be utilized in other various down hole drilling apparatuses, devices, or systems. Generally, the drilling tool connection formed in part by the male pin 205, the female box 225, and the locking pin 265 may be used to couple various sections of a downhole drilling apparatus such as, for example a downhole drilling motor, bearing mandrel, universal assembly joint, and drill bit, to name but a few.

Turning particularly to FIG. 2A, a side view and cross-sectional view of the male pin 205 is illustrated. The male pin 205, generally, is an elongated shaft of, for example, machined steel, which transmits torque generated by a downhole drilling motor to the female box 225 shown in FIG. 2B. The male pin 205 includes a longitudinal pin bore 210 disposed along a longitudinal axis of the male pin 205 and a pin perimeter 215 defining all outer shape of the male pin 205. In some implementations, the pin perimeter 215 is substantially hexagonal in shape, thereby providing six substantially flat outer surfaces of the male pill 205. The pin perimeter 215, thus, provides the surface from which the torque is transmitted to the female box 225. The pin perimeter 215, however, may be alternatively shaped in various other geometric configurations. For instance, the pin perimeter 215 may be substantially octagonal, decagonal (i.e., ten-sided), or nonagonal (i.e., nine-sided). Regardless, the pin perimeter 215 may be a geometric shape having an equivalent number of sides in the male pin 205 and the internal configuration of female box 225.

Pin bore 210 includes a pin circumference 207 (i.e., a cylindrical interior surface), which extends the length of the male pin 205. In some implementations, the pin circumference 207 is substantially smooth to provide a reduced-friction surface for drilling fluid to flow past. The pin circumference 207 also defines the pin bore 210. The pin bore 210 extends through the male pin 205 such that a longitudinal axis of the pin bore 210 is aligned with a longitudinal axis of the male pin 205 itself. In some implementations, the pin bore 210 is substantially cylindrical with a substantially circular cross-sectional area. Alternatively, the pin bore 210 (and pin circumference 207) may be any appropriate shape for the drilling application. During downhole drilling operations, a drilling fluid used to, for example, provide hydraulic power to the downhole drilling motor, cool the drilling bit as it drills a geological formation and return drilled cuttings to the surface through an annulus between the well bore and the drill string, may flow through the pill bore 210. Thus, in some embodiments, the pin bore 210 may provide a raceway for drilling fluid communication between and among downhole drilling devices.

The male pin 205 includes at least one locking pin slot 220. For example, the embodiment of the male pill 205 illustrated in FIG. 2A includes two locking pill slots 220. The locking pin slots 220 are formed in the pin perimeter 215 near an end of the male pill 205 including a pin boss 223. The locking pin slots 220 may, in some embodiments, be cast/forged in the male pin 205. Alternatively, the locking pin slots 220 may be machined in the male pin 205 after manufacture. As described below in more detail with reference to FIG. 3, each locking pin slot 220 may at least partially receive a locking pin designed to couple the male pin 205 and a female box (such as the female box 225 shown in FIG. 2B) together.

Locking pin slots 220, as illustrated, may be semi-cylindrical in shape, thereby creating a cutout through a width of the male pin 205 extending transverse to the longitudinal axis of the male pin 205. Alternatively, the locking pin slots 220 may form cutouts through the male pin 205 having any appropriate cross-sectional area, such as, for example, triangular, square, or rectangular.

Turning now to FIG. 2B, this figure illustrates a side view and cross-sectional view of the female box 225 of the drilling tool connection. The female box 225 includes a box aperture 227 defined by a box circumference 235, a box perimeter 230, and one or more box bores 240 disposed in the box circumference 235. Generally, the female box 225 receives the male pin 205 into the box aperture 227 until the pin boss 223 butts against a box shoulder 245, such that the locking pin slots 220 and box bores 240 are substantially aligned, forming substantially cylindrical apertures transverse to the longitudinal axes of the male pin 205 and female box 225. The female box 225, further, includes a box connector 260, which may be coupled to another downhole drilling device, such as a drill bit section, universal joint assembly, a bearing section, or a downhole drilling motor, to name a few. In some embodiments, the box connector 260 may be a threaded-type connection, but the box connector 260 may be any appropriate type of connection depending on, for instance, the type of downhole drilling device coupled or connected to the female box 225.

The box perimeter 230, in some embodiments, is substantially circular thereby giving the female box 225 a substantially circular cross-sectional area. Disposed within the female box 225 through at least a portion of a longitudinal length of the female box 225 is the box aperture 227. The box aperture 227 extends from a distal end of the female box 225 towards the box shoulder 245. Typically, the box aperture 227 is shaped to substantially mate to the shape of the pin perimeter 215, thereby allowing the box aperture 227 to securely receive the male pin 205. Further, the box aperture 227 may be shaped or sized for minimal tolerance between the pin perimeter 215 and the box circumference 235. In such fashion, a concentricity between the male pin 205 and the female box 225 may be achieved. The shape of the box aperture 227, as illustrated in FIG. 2B, may be substantially hexagonal to mate to the pin perimeter 215. Alternatively, the shape of the box aperture 227 may be substantially octagonal, decagonal (i.e., ten-sided), or nonagonal (i.e., nine-sided). In any event, in some embodiments, the pin perimeter 215 and the box aperture 227 may be substantially identical in shape.

In some embodiments of the female box 225, one or more seal grooves 255 may be formed in the box circumference 235. For example, FIG. 2B illustrates one embodiment of the female box 225 having two seal grooves 255 machined into the box circumference 235. Alternatively, more (or fewer) seal grooves may be utilized. The seal grooves 255, typically, are disposed around the entire box circumference 235 and receive a box seal 250 therein. The box seal 250 may be a continuous ring having substantially circular cross-section and formed of rubber, neoprene, or other pliable material. In some implementations, the box seal 250 may alternatively be integral to or part of the male pin 205. In any event, the box seal 250 may operate in substantially similar fashion regardless of whether it is included as part of the male pin 205 or female box 225.

In operation, the box seal 250 may be in substantially constant contact with the female box 225 and the male pin 205 when the male pin 205 is inserted into the box aperture 227 and coupled to the female box 225, thereby providing a fluid-tight seal between the male pin 205 and the female box 225. Fluid, such as drilling fluid, therefore, may be substantially prevented from entering the box aperture 227 due to the box seal 250 during drilling operations or also during non-activity of the downhole drilling apparatus (e.g., trips into or out of the well bore).

The female box 225 also includes one or more box bores 240 disposed through the female box 225 transverse to the longitudinal axis of the female box 225. For example, some embodiments of the female box 225 may include two box bores 240, as illustrated in FIG. 2B. Alternatively, more or fewer box bores may be formed in a box, such as the female box 225. Typically, when the male pin 205 is inserted into the box aperture 227 such that the pin boss 223 rests against the box shoulder 245, the locking pin slots 220 are substantially aligned with the locking slot 240. When aligned or substantially aligned, each locking pin slot 220 and corresponding box locking slot 240 for, for example, a substantially cylindrical aperture transversely disposed through the male pin 205 and female box 225. As described more fully with reference to FIG. 2C, a locking pin may then be inserted through the substantially cylindrical aperture defined by the slots 220 and bore 240. As with the locking pin slots 220, the box bores 240 may be substantially semi-cylindrical in shape, thereby creating a cutout through the width of the female box 225. Alternatively, the box bores 240 may form cutouts through the female box 225 having any appropriate cross-sectional area, such as, for example, triangular, square, or rectangular. Regardless, in their usual configurations, the locking pin slots 220 and the locking slot 240 have substantially identical cross-sectional areas.

FIG. 2C illustrates a side view and cross-sectional view of a locking pin 265. The locking pin 265, typically, is inserted through an aperture defined by the pin slot 220 and the corresponding locking slot 240 when the male pin 205 is inserted into the box aperture 227 such that the pin boss 223 is in contact with the box shoulder 245. In some embodiments, as described above, the male pin 205 includes two locking pin slots 220 and the female box 225 includes two box bores 240. In such embodiments, generally, two locking pins 265 may be used such that a single locking pin 265 is inserted through each aperture defined by a particular pin slot 220 and corresponding locking slot 240. The locking pin 265 may be made of a high-strength material such as, for example, stainless steel, titanium, or other alloy steel. Regardless, in certain embodiments, the locking pin 265 may have good shear strength characteristics. For instance, in some implementations, the locking pin 265 may bear all or substantially all of an axial force transmitted to the male pin 205 in order to pull the downhole drilling apparatus out of the well bore. The locking pin 265, therefore, may exhibit a high shear strength to withstand the axial force in order to keep the male pin 205 and the female box 225 coupled during the drilling apparatus trip out of the well bore.

The locking pin 265 is illustrated with a substantially circular cross-section, thereby making it insertable into the aperture defined by the pin slot 220 and the corresponding locking slot 240 as illustrated in FIGS. 2A-B. Alternatively, the locking pin 265 may have any appropriate cross-sectional configuration depending on the configurations of the locking pin slots 220 and the box bores 240. As one example, if the aperture defined by the pin slot 220 and the corresponding locking slot 240 is substantially square in cross-section upon alignment of the male pin 205 into the box aperture 227, then the locking pin 265 may have a substantially square cross-section as well. Generally, the locking pill 265 may be designated to be inserted into such an aperture with little tolerance, thereby ensuring a snug fit within the aperture. In such embodiments (as well as others), lubricant may be applied to tie locking pin 265 in order to insert it into the aperture.

FIG. 3 illustrates a portion of a downhole drilling apparatus 300 incorporating a drilling tool connection 301 in accordance with the present disclosure. The downhole drilling apparatus 300 includes a downhole tool 380, a drilling tool connection 301 and a drill bit 375. Generally, the drilling tool connection 301 couples the downhole tool 380 with the drill bit 375 and transmits rotational torque generated by a downhole drilling motor to the drill bit 375 during drilling operations. Further, the drilling tool connection 301 may transmit an upward axial force to the drill bit 375 when the downhole drilling apparatus 300 is pulled out of a well bore such that the drill bit 375 remains coupled to the downhole tool 380. Alternatively, a downward force maybe transmitted via the tool connection 301. In certain embodiments, the drilling tool connection 301 may be substantially similar to the drilling tool connection 135 illustrated in FIG. 1, as well as a drilling tool connection including a pin, a box, and one or more locking pins as those components are illustrated in FIGS. 2A-C.

The drilling tool connection 301 includes a male pin 305, a female box 325, one or more locking pins 365, and one or more end caps 370. Generally, such components of the drilling tool connection 301, for example, the male pin 305, the female box 325, and the locking pin 365, may be substantially similar to corresponding components described with reference to FIGS. 2A-C. FIG. 3 illustrates the male pin 305 inserted into a box aperture 327 such that a pin boss 323 is proximate to with a box shoulder 345. Further, two locking pins 365 are inserted into the apertures defined by locking pin slots 320 and corresponding box bore 340 upon alignment of the locking pin slots 320 and the box bores 340. End caps 370 are coupled to each end of the locking pins 365, thereby securing the locking pins 365 within the apertures. When secured, the male pin 305 and the female box 325 are securely coupled together during all movement of the drilling tool connection 301, such as rotational movement during a drilling operation or axial movement (e.g., movement substantially parallel to the well bore) during trips in or out of the well bore.

More specifically, the male pin 305 may be substantially hexagonal in cross-sectional shape with a substantially circular longitudinal bore 310 aligned with a longitudinal axis of the male pin 305. The longitudinal bore 310 (as well as the box aperture 327) may, for example, provide a channel through which drilling fluid flows to the drill bit 375 from the downhole drilling motor, thereby cooling the drill bit 375 and removing drilled cuttings from the bit 375. Further, the male pin 305 may also include a secondary outer circumference 382, which is at least slightly greater in dimension than the portion of the male pin 305 inserted into the box aperture 327. In some embodiments, for example, the secondary outer circumference 382 may be sized such that when the male pin 305 is inserted into the box aperture 327, the secondary outer circumference 382 may stop against a box ledge 385 formed in the female box 325. In such a fashion, the six substantially planar outer surfaces of the male pin 305 may transmit all or substantially all of the rotational torque generated by the downhole drilling motor to the female box 325 and, therefore, the drill bit 375.

As noted above, when the male pin 305 is fully inserted into the box aperture 327, the locking pin slots 320 are aligned with the box bores 340, thereby allowing the locking pins 365 to be inserted into the apertures defined by the slots 320 and bores 340. The end caps 370 may then be attached to the distal ends of the locking pins 365. For instance, the end caps may be threaded onto the locking pins 365 (e.g., male/female NPT) or snapped into place through an alternate coupling mechanism (e.g., set screws or snap rings) as appropriate. Regardless, the end caps 370 may securely attach to the distal ends of the locking pins 365 to ensure that the locking pins 365 may not be removed or come Out of the apertures in which the pins 365 reside during drilling operations. In some embodiments, the end caps 370 may require a specialized tool for attachment to and removal from the locking pins 365.

The female box 325 includes the box aperture 327 to receive the male pin 305, as well as a box connector 360. The box connector 360 may allow a downhole tool, such as the drill bit 375, to be coupled to the drilling tool connection 301. The female box 325 also includes the box shoulder 345, which may absorb an axial thrust force transmitted through the pin boss 323 and transmit such force to the drill bit 375. For example, a drill string which includes the downhole drilling apparatus 300 may include multiple sections of drill pipe extending to the surface and multiple drill collars attached to such drill pipe closer to the downhole drilling apparatus 300. The drill collars may, by design, exert a downward axial force on the downhole drilling apparatus 300 due to the weight of the drill collars. In such fashion, the drill bit 375 may be urged deeper into a subterranean formation. Such axial force, in some embodiments of the drilling tool connection 301, may be transmitted through the box shoulder 345 to the drill bit 375 rather than, for example, the locking pins 365. In such embodiments, the locking pins 365 may be utilized to withstand a shear force applied to such locking pins 365 and keep the male pin 305 coupled to the female box 325 when the downhole drilling apparatus 300 is removed from the well bore.

FIG. 4 illustrates one method 400 of assembling a drilling tool connection in accordance with the present disclosure. Method 400 may be used with, for example, the drilling tool connection 135 shown in FIG. 1, the drilling tool connection including the male pin 205, the female box 225, and the locking pins 265 illustrated in FIGS. 2A-C, or the drilling tool connection 301 shown in FIG. 3. In any event, method 400, alternatively, may be used with other embodiments of a drilling tool connection according to the present disclosure including such components as a pin, a box, one or more locking pins, and one or more end caps. Method 400 may begin with a user of the drilling tool connection lubricating the surfaces of the drilling tool connection components [402]. For example, the user may lubricate the outer surface of the pin, the inner surface of the box, the locking pins, as well as the pin slots and the box bores. In such fashion, these components may be more easily assembled while ensuring tight tolerances between the components.

The user may then insert the pin into the box aperture [404]. After the pin is inserted into the box aperture, the user may locate a pin boss on the pin proximate to a box shoulder of the box [406]. Such proximity may ensure, for example, that rotational torque generated by a downhole drilling motor and transmitted to the pin is further transmitted to the box primarily through substantially planar outer surfaces of the pin. Such proximity may also ensure a correct alignment of the pin slots and the box bores, but in any event, the user may align the pin slots with the box bores [408]. For example, the pin slots and the box bores may be semi-cylindrical and be disposed through the pin and the box, respectively, transverse to longitudinal axes of the pin and the box. When aligned properly, the pin slots and the box bores may define substantially cylindrical apertures. Alternatively, the pin slots and the box bores, when aligned properly, may define apertures of different cross-sectional configurations (e.g., square, rectangular) depending on the shape of the pin slots and the box bores.

Continuing with method 400, the user may then insert locking pins into the apertures defined by the aligned pin slots and box bores [410]. For instance, the locking pins may be substantially cylindrical to fit into such apertures defined by the semi-cylindrical pin slots and box bores. The user may then secure end caps to the end portions of the locking pins

For instance, the ends caps may be threaded or snapped into place on the locking pins, thus preventing the locking pins from being removed from the apertures. Next, the user may then couple the assembled drilling tool connection to one or more downhole tools [414]. In some cases, the downhole tool may be a downhole drilling motor, a drill bit, a universal joint assembly, and the like.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, method 400 may include more or fewer steps without departing from the present disclosure. Further, the illustrated steps of method 400 may be performed in substantially the same order presented or in various other orders, as appropriate. Accordingly, other implementations are within the scope of the following claims. 

1. A drilling tool connection, comprising: a male pin connector element disposed on a first downhole drilling device, the male pin connector element comprising a substantially hexagonal outer perimeter, at least a portion of the pin having a substantially cylindrical bore along a longitudinal axis of the pin, the pin having at least one transverse slot formed transverse to the longitudinal axis of the pin; a female box connector element disposed on a second downhole drilling device comprising a substantially circular outer perimeter at least a portion of the box having a substantially hexagonal aperture aligned with a longitudinal axis of the box, the box having at least one transverse bore formed in the box transverse to the longitudinal axis of the box, the substantially hexagonal aperture of the female box adapted to receive the substantial hexagonal portions of the male pin; and a locking pin insertable through an aperture defined by the at least one transverse slot of the pin and the at least one transverse bore of the box upon alignment of the transverse slot with the transverse bore.
 2. The drilling tool connection of claim 1, wherein the substantially cylindrical longitudinal aperture is adapted to direct drilling fluid through the second downhole drilling device.
 3. The drilling tool connection of claim 1, wherein the locking pin is substantially cylindrical.
 4. The drilling tool connection of claim 1 further comprising an end cap configured to fasten to the locking pin and substantially prevent the locking pin from being removed from the aperture defined by the transverse slot and the transverse bore.
 5. The drilling tool connection of claim 1, further comprising an end cap configured to fasten to the aperture formed by the transverse slot and the transverse bore by a threaded connection.
 6. The drilling tool connection of claim 1, wherein the aperture defined by the transverse slot and the transverse bore is substantially cylindrical.
 7. The drilling tool connection of claim 1 further comprising a first box seal disposed within a box seal groove, the box seal groove formed in an interior surface of the box defining the substantially hexagonal aperture.
 8. The drilling tool connection of claim 1, wherein the locking pin is a first locking pin, the drilling tool connection further comprising: a second transverse slot formed proximal to the distal end of the pin transverse to the longitudinal axis of the pin; a second transverse bore formed in the box transverse to the longitudinal axis of the box; and a second locking pin insertable through a second aperture defined by the second transverse slot and the second transverse bore upon alignment of the second transverse slot with the second transverse bore.
 9. The drilling, tool connection of claim 1, wherein the first downhole drilling device is selected from the group consisting of: a downhole drilling motor; a stabilizer; a universal joint assembly; a drill bit; a drill collar; a drill pipe; or a bearing mandrel.
 10. The drilling tool connection of claim 1, wherein the second downhole drilling device is selected form the group consisting of: a downhole drilling motor; a stabilizer; a universal joint assembly; a drill bit; or a bearing mandrel.
 11. The drilling tool connection of claim 1, wherein the box further comprises a shoulder formed in the box at a distal end of the substantially hexagonal aperture and the pin further comprises a substantially planar surface formed at the distal end of the pin and configured to transmit thrust to the shoulder substantially parallel to the longitudinal axes of the pin and the box.
 12. A well bore tool coupling device, comprising: a male pin disposed on a first downhole drilling device, the male pin comprising a pin perimeter of a first geometric shape, at least a portion of the pin having a substantially cylindrical bore along a longitudinal axis of the pin, the pin having at least one transverse slot formed in the pin perimeter transverse to the longitudinal axis of the pin; a female box connector element disposed on a second downhole drilling device comprising at least a portion of the box having a box aperture of a second geometric shape aligned with a longitudinal axis of the box, said box aperture adapted to receive the first geometric shape portion of the male pin, the box having at least one transverse bore formed in the box transverse to the longitudinal axis of the box; and a locking pin insertable into an aperture defined by the at least one transverse slot of the pin and the at least one transverse bore of the box upon alignment of the transverse slot with the transverse bore.
 13. The well bore tool coupling device of claim 12, wherein the first and second geometric shapes selected from the group consisting of: a hexagon; an octagon; a nonagon; or a decagon.
 14. The well bore tool coupling device of claim 12, wherein the longitudinal aperture is adapted to direct drilling fluid through the second downhole drilling device.
 15. The well bore tool coupling device of claim 12 further comprising an end cap configured to fasten to the locking pin and substantially prevent the locking pin from being removed from the aperture defined by the transverse slot and the transverse bore.
 16. The well bore tool coupling device of claim 12, further comprising an end cap configured to fasten to the aperture formed by the transverse slot and transverse bore by a threaded connection.
 17. The well bore tool coupling device of claim 12, wherein the aperture defined by the transverse slot and the transverse bore is substantially cylindrical.
 18. The well bore tool coupling device of claim 12 further comprising a first box seal disposed within a box seal groove, the box seal groove formed in an interior surface of the box defining the box aperture.
 19. The well bore tool coupling device of claim 12, wherein the locking pin is a first locking pin, the well bore tool coupling device further comprising: a second transverse slot formed at the distal end of the pin transverse to the longitudinal axis of the pin; a second transverse bore formed in the box transverse to the longitudinal axis of the box; and a second locking pin insertable through a second aperture defined by the second transverse slot and the second transverse bore upon alignment of the second transverse slot with the second transverse bore.
 20. The well bore tool coupling device of claim 12, wherein the female box connector element further comprises a shoulder formed in the box at a distal end of the aperture of the second geometric shape and the pin further comprises a substantially planar surface formed at the distal end of the pin and configured to transmit thrust to the shoulder substantially parallel to the longitudinal axes of the pin and the box connector element.
 21. The well bore tool coupling device of claim 12, wherein the female box connector element further comprises a ledge proximate to a distal end of the box connector element. 